Answer: The savings per movie with the pass is $3.50 - $1.00 = $2.50. For the pass to benefit Seth's father, Seth must attend enough movies such that the total savings is equal to or greater than $40.
Let's call x the number of times Seth must attend for the pass to benefit his father. Then:
$2.50x >= $40
Solving for x:
$2.50x/$2.50 >= $40/$2.50
x >= 16
So Seth must attend at least 16 movies in order for the pass to benefit his father.